The California Regional Primate Research Center (CRPRC) has served for a number of years as a centralized Primate Testing Facility (PTF) for the Contraceptive Development Branch (CDB) of the National Institute of Child Health and Human Development (NICHHD). The purpose of this contract is to house and maintain a colony of cynomolgus monkeys (Macaca fascicularis) as well as use them in the conduct of experiments designed to test the safety and efficacy of contraceptive agents prior to being tested in humans. The cynomolgus monkey was chosen for these studies because of its size, lack of seasonality and its similarity to humans in many aspects of reproductive function. All animals are maintained under normal CRPRC guidelines of animal care. At the present time most agents being tested are synthetic steroids which exhibit either progestational or androgenic activities. In addition, one study evaluated a sperm protein for use as a potential immuno-contraceptive vaccine. Future studies will include a pharmacokinetic evaluation of a topical estrogen cream as a potential estrogen replacement therapy for women, and additional study of immuno-contraceptive vaccines. *KEY*Cynomolgus macaque, Steroidal contraception, Immuno-contraception